If the Tories hoped to avoid the widespread web mockery that greeted their "airbrushed" David Cameron poster when they launched three new adverts yesterday, they failed completely. Within minutes, doctored versions of the "I've never voted Tory before, but ... " posters were being uploaded to websites such as mydavidcameron.com – which led the pack last time – and IveNeverVotedTory, as well as Facebook.

But did they actually want to avoid this? They made it so easy for internet pranksters to repeat the trick. The new posters feature three presentable young-ish people, one black, one working class, one a mother, and all start with the same half-sentence, which practically begs to be completed in a mischievous manner – as can be seen by the number of people who have done so without any reference to the pictures at all on Twitter, where the search term #ivenevervotedtory was a big hit yesterday and has already resulted in controversy. (Today #i'venevervotedlabour is doing good business too.)

The Tories set out their slogan on big blue oblongs that you could comfortably edit using Microsoft Paint, never mind Photoshop. Have they simply calculated that all publicity is good publicity? The downside of the flurry of online adaptations is a pretty clear reminder that some voters still consider the Conservatives the "nasty party" ("I've never voted Tory before, and never would because that evil cow stole my milk"), but to be honest many of the doctored posters' attacks are fairly tame.

The upside for Cameron and co is a massive free media blitz every time they release a new poster. And at the most basic level all the mockery probably helps the simple messages the Conservatives want to express – we have a fairly normal-looking leader at last, we actively want different types of people to support us – to lodge themselves in the public mind.

Presumably when Labour begins its poster campaign its adverts will be altered online too. But Gordon Brown's team will be carefully assessing whether any such doctoring is the product of genuine mass enthusiasm (as the "airbrushed" Cameron adverts, particularly, seemed to be) or are being produced and forwarded on only by committed anti-Labourites.

Anyway, here are some of my favourites of the current crop of doctored posters.